1. Field of the Invention
The present invention relates generally to a probe cartridge assembly including a probe for analyzing an environment, and a multi-probe assembly including at least one such probe cartridge assembly.
2. Discussion of the Background
Electric probes are measurement tools used in the characterization of low temperature plasmas like those used in the semiconductor manufacturing industry. Electric probes have been utilized in a variety of configurations and geometric shapes. Each configuration and geometry has advantages and disadvantages compared to the others. One such configuration is the single, cylindrical probe, called a Single Langmuir Probe.
An example of such a single probe is constructed of tungsten wire housed in a quartz tube. The quartz tube is 0.25 inches in outer diameter. The 0.030-inch diameter tungsten wire extends approximately 0.076 inches beyond the end of the quartz tube, forming a probe tip with a surface area of 0.05 cm2 exposed to the plasma. The probe is inserted into the plasma through a vacuum bellows, which allows linear translation of the probe tip through the plasma in one direction only. The probe tip is maintained at 5 mm above the surface of the chuck. The procedure used by the inventors has been to record the probe current-voltage characteristics at the center of the chuck, and at one-inch intervals from the center to the edge, e.g., 0, 1, 2, 3 and 4 inches from the center for an 8-inch wafer.
The inventors have determined that because the single probe arrangement is mounted in a fixed azmithal position in a feedthrough on the side of the chamber, measurements along different (azmithal) axes require the physical repositioning (rotation) of the source. Before a new set of measurements can be made numerous mechanical operations must be performed, including removing all fluid and electrical connections, and venting the system to atmosphere. It has been the inventors' experience that these mechanical operations consume several hours for each new axis of rotation. A set of probe measurements from center to edge in four directions (+x to −x, and +y to −y) can take more than a full day using a single probe. In addition, each time the source is vented and physically repositioned there is a potential to introduce measurement inconsistencies due to small variations in the physical repositioning of the source, and the vertical position of the probe with respect to the chuck and the bottom of the source.
In an effort to eliminate these potential sources of error and to reduce the total measurement time, the inventors have constructed a multi-probe assembly including a probe cartridge assembly as described below.